Materi : Barisan dan Geometri
x => U3 = a + 2b = 9
y => U5 + U7 = 2a + 10b = 36 atau
a + 5b = 18
Nilai Beda
( y - x ) = Uy - Ux
5b - 2b = 18 - 9
3b = 9
b = 3
Nilai Suku Pertama
a = Ux - [ x - 1 ]b
a = 9 - [ 3 - 1 ]3
a = 9 - 2(3)
a = 9 - 6
a = 3
Pola barisan aritmatika
3, 6, 9, ...
Suku Pertama = 3 , Beda = 3
Maka Rumus Pola : Un = 3n
Maka U10 = 3(10) = 30
Sn = n/2( a + Un )
S10 = 10/2( 3 + U10 )
S10 = 5( 3 + 30 )
S10 = 15 + 150
S10 = 165
Semoga bisa membantu
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Materi : Barisan dan Geometri
x => U3 = a + 2b = 9
y => U5 + U7 = 2a + 10b = 36 atau
a + 5b = 18
Nilai Beda
( y - x ) = Uy - Ux
5b - 2b = 18 - 9
3b = 9
b = 3
Nilai Suku Pertama
a = Ux - [ x - 1 ]b
a = 9 - [ 3 - 1 ]3
a = 9 - 2(3)
a = 9 - 6
a = 3
Hasil / Result :
Pola barisan aritmatika
3, 6, 9, ...
Suku Pertama = 3 , Beda = 3
Maka Rumus Pola : Un = 3n
Maka U10 = 3(10) = 30
Jumlah 10 Suku Pertama
Sn = n/2( a + Un )
S10 = 10/2( 3 + U10 )
S10 = 5( 3 + 30 )
S10 = 15 + 150
S10 = 165
Semoga bisa membantu